Vitit Muntarbhorn in a letter he sent U.N. Human Rights Council President Joaquín Alexander Maza Martelli on Sept. 8 cited his personal health and that of a family member.

“The main reason for the resignation is illness: I have been unwell for the past few months and have also been hospitalized,” wrote Muntarbhorn. “I am now recovering and I wish to reduce my workload generally. In addition, there is a family reason: A key member of my family/household is ill and I am now having to undertake additional family obligations which consume both time and energy.”

Muntarbhorn — an international law professor at Chulalongkorn University in Bangkok — has been in the position since last fall.

The U.N. Human Rights Council in June 2016 approved a resolution that created the position.

A U.N. committee last November rejected a proposal that would have suspended Muntarbhorn. The U.S. is among the more than 80 countries that voted against a second motion against his position a few weeks later.

Muntarbhorn in his resignation letter notes he has submitted two reports on efforts to combat violence and discrimination based on sexual orientation and gender identity to the U.N. Human Rights Council and the U.N. General Assembly. He also said he is continuing to work on a report about Argentina.

“The mandate is to address the issues of violence and discrimination,” Muntarbhorn told the Washington Blade in January during a telephone interview from Geneva. “That’s the entry point.”

Muntarbhorn in May spoke at the closing plenary of the Out Games Miami Human Rights Conference that took place in Miami Beach, Fla.

Muntarbhorn’s resignation is tentatively scheduled to take effect on Oct. 31. It is not immediately clear when the process to name Muntarbhorn’s successor will begin.

“We are saddened by Vitit’s departure, and our thoughts are with him and his family,” Jessica Stern, executive director of OutRight Action International, a global LGBTI advocacy group, told the Blade on Tuesday in a statement. “Vitit’s work was only just beginning. Nonetheless, he laid a strong foundation by publishing two U.N. reports documenting LGBTI rights violations and progress globally.”

“Of course, even independent experts sometimes have personal emergencies,” she added. “The mandate from the U.N. remains and work will continue. OutRight will work with civil society and U.N. members to encourage the recruitment of an equally capable successor.”